Magnetic stirring element

ABSTRACT

A combination weighing and mixing device adapted for use as the mixing element of a magnetic stirring apparatus including a container and magnetic drive means for rotating the mixing element in the container, said device comprising a generally ellipsoidally-shaped housing, a magnetic element encapsulated in said housing and at least one cavity formed in said housing defining a measuring chamber for additives to be mixed with a liquid in the container.

United States Patent Landsberger July 31, 1973 1 1 MAGNETIC STIRRINGELEMENT 2,951,689 9/1960 Asp et al 259/DIG. 46

[76] Inventor: Kurt Landsberger, c/o Bel-Art Products, Pequannock, NJ.07440 Prlmary Examiner-Wuhan Pnce Assistant ExaminerAlan l. CantorFiledi J y 1971 Att0mey-Howson and Howson [21] Appl. No.: 161,009

[5 7] ABSTRACT 52 us. Cl. 259/1 R, 23/252 R, 259/50, A combinationWeighing and mixing device adapted for 259/102, 5 46 use as the mixingelement of a magnetic stirring appara- 51 1111. c1 B011 13/08 includinga container and magnetic drive means for [58] Field of Search 259/DIG.46, 5, 21, rotating the mixing element in the container, Said 59 4 5023/252 R vice comprising a generally ellipsoidally-shaped housing, amagnetic element encapsulated in said housing 5 References Cited and atleast one cavity formed in said housing defining UNITED STATES PATENTS ameasuring chamber for additives to be mixed with a liquid in thecontainer. 2,518,758 8/1950 Cook 259/DlG. 46 2,699,378 1/1955 Koelle259/D1G. 46 4 Claims, 5 Drawing Figures MAGNETIC STIRRING ELEMENT Thepresent invention relates broadly to mixing apparatus, and morespecifically to a combination mixing and measuring device for use inmagnetic stirring apparatus.

The present invention is especially adapted for use in laboratoryprocedures where magnetic stirring apparatus are used for mixing orblending various components of a composition. These apparatus generallyinclude a support structure for a mixing container or the like and amagnetic bar suitably mounted for rotation adjacent the base of thecontainer to produce a magnetic field operable to effect actuation of amagnetic elementin the container, usually in the form ofastirring ormixing bar. v}

Typically in the use of these magnetic stirring apparatus, apredetermined quantity of at least one of the constituents is weighed ormeasured in a separate implement such as a weighing dish, scoop orcontainer and then emptied into the mixing container. This system hascertain disadvantages and drawbacks which the present inventionisdesigned to resolve. For example, it has been found that theseconventional procedures are not totally satisfactory in mixing liquidconstituents of a composition where the precise quantities of theconstituents must be measured. For example, addition of a predeterminedsmall accurate volume is difficult since the liquid normally adheres tothe utensil in which it is measured, necessitating washing the utensilwith a suitable'liquid' and adding the washings to the mixing containerin order to transfer all of the liquid ingredient -to be added; This isdisadvantageous, of course, when the.added volume of the wash liquidwould be undesirable. In addition, such adhesion of additives tomeasuring or transfer implement can be costly where the additives areprecious materials and can not be completely emptied into the mixingcontainer. Further, the presently known system presents the risk ofintroducing foreign substances, in the wash liquid, for example, whichin some instances may contaminate the final composition.

The present invention provides a new and useful combination measuringand stirring device, particularly adapted for use in magnetic mixingapparatus ofthe type discussed above. The device of the presentinvention consists of a magnetic element housed in a generallyellipsoidally-shaped housing preferably made of a low-friction, inertmaterial. The housing is provided with at least one'cavity defining ameasuring chamber of predetermined volumetric capacity and a flat seatdiametrically opposed to the cavity so that the device may be supportedon a flat surface for filling the measuring chamber with a desiredamount of additive. The device is constructed so that it rotates on itsside with the cavity disposed transversely to the axis of rotation. Inthis manner, with the normal spinning attitude of the device on itsside, the cavity is open to the stirring action of the fluid in themixing container.

The mixing and measuring device of the present invention is designed foruse in the following manner. The user places the tared device on a flatsurface of a scale and fills the cavity with the precise measuredquantity of an additive to be mixed. The device is deposited into themixing container and then placed on a magnetic mixing apparatus. Thefield created by the mixer magnet effects rotation of the device on itsside,

thereby positioning the cavity in the best position to be exposed to themixing action of the fluid in the container. Thus, the device of thepresent invention eliminates the problems of inaccuracy due to adhesionof additives to transfer equipment of addition of wash liquid and alsoeliminates the problem of waste which is important, particularly wherethe additives are precious materials.

These and other objects of the present invention and the various detailsof the operation and the construction thereof are hereinafter more fullyset forth with reference to the accompanying drawings, wherein:

FIG. 1 is a side view partly in section of a magnetic mixing apparatuswith a measuring and mixing device of the present invention in anoperative position;

FIG. 2 is a side view of the measuring and mixing device of the presentinvention with parts broken away to show the construction more clearly;

FIG. 3 is a plan view of the device; and

FIGS. 4 and 5 are sectional views taken on lines 4-4 and 5-5 of pages 1and 2 respectively.

Referring now to the drawings and particularly to FIG. 1 thereof, thereis illustrated a conventional magnetic stirring apparatus 10 for whichthe mixing and measuring device 12 of the present invention is adaptedfor use. The magnetic stirring apparatus 10 includes a support structure14 including a flat base on which a container 16 for the liquids to bemixed is supported. The apparatus includes a rotatably mounted magneticbar 18 actuatable by a motor 20 to produce a magnet field to effectrotation of the mixing and measuring device 12 of the present inventionin the container 16.

The mixing and measuring device 12 of the present invention comprises anelongatedbar magnet 20 encapsulated in a generally ellipsoidally-shapedhousing 22 preferably made of a low-friction, inert material such as atetrafluoroethylene polymer. The housing is formed with a flat base asat 26 and at least one measuring chamber or cavity diametrically opposedto the base 26. In the present instance, there is one measuring chamber27 defined by a cavity30 in the housing terminating in an upwardlyprojecting oval-shaped peripheral lip 32. The bottom wall 33 of thechamber is flat, parallel to the base 26 and merges with they lip 32 ina radiused side wall 35. The plane of the upper edge of the lipis alsoparallel to the base 26. I

In the present instance, the device is constructed in such a manner thatits normal spinning attitude in the mixing container is on its side,that is about an axis A, normal to the axis A through the center of themeasuring chamber 27. In the present instance, this is accomplished byoffsetting the center of gravity C of the device from the center C of atruly ellipsoidal shape of the device. In other words, the cylindricalbar magnet 20 is disposed in the housing so that it is symmetrical withrespect to a longitudinal plane PP through the center C dividing thedevice into upper and lower sections 12a and 12b respectively. The barmagnet 20 is also symmetrical relative to planes P,P and P P through thecenter C transverse to the plane PP. As illustrated, the major and minoraxes of the generally ovalshaped measuring chamber 27 and base 26 arealigned with the axes of the section through the center of the devicedefined by the plane PP. By this arrangement the device is trulysymmetrical relative to planes P,-P, and P -P and that except for themeasuring chamber and flat base, would be symmetrical about the planeP-P. Accordingly, since the volume of measuring chamber cavity 30 isgreater than the volume enclosed between the arcuate trace of the lowersection 12b of the housing and the flat base 26, there is a greaterconcentration of mass in the lower section 12b and the cen ter ofgravity C is therefore located in the lower section 12b on the axis A toone side of the longitudinal plane P-P. Note that the planes PP, P,P,and P l are taken through the device at points of greatest crosssection; that is, the elliptical sections defined by the planes P-P andP,--l=' have the greatest major and minor axes and the trace of thecircular section defined by plane P -l has the greatest diameter.

Accordingly, when the device is placed in the liquid in the mixingcontainer 16, it will assume a spinning attitude about the axis A, whena magnetic field is created on rotation of the magnet 18 of the magneticstirring apparatus. This spin attitude is effected by means of theinteraction of centrifugal force with the constrained movement of themagnet 18 in the rotating magnetic field. In this position as notedpreviously, the measuring chamber 27 faces sideways to the central axisof the container and the additive therein is subjected to the stirringaction of the liquid, thus insuring complete mixing of the additive intothe larger volume of liquid.

Thus, in using the device of the present invention, the tared device 12is placed on a scale and then the desired measured quantity of additiveis deposited into the mixing chamber 27. Thereafter, the device 12 isplaced into the container 16 with the larger volume of liquid to bemixed with the additive, and the magnetic stirring apparatus isactuated. Then as noted above, the device is rotated on the axis A,whereby thorough mixing of the additive with the larger volume of liquidin the container is effected. Accordingly, by the present invention,accurately measured amounts of additives can be added to a larger volumeof liquid without incurring any loss in the transfer or introducing anyforeign inert materials into the mixture and thorough mixing results.

I claim: g

l. A combination weighing and mixing device adapted for use as themixing element of a magnetic stirring apparatus including a containerand magnetic drive means for rotating the mixing element in thecontainer, said device comprising a generally ellipsoidallyshapedhousing, at least one cavity formed in said-housing defining a measuringchamber for additives to be mixed with a liquid in the container, saidhousing including a flat base section formed in the housingdiametrically opposed to the measuring chamber and parallel to the planethrough the upper edge of the measuring chamber, and a magnetic elementencapsulated in said housing.

2. The device as claimed in claim 1 wherein said housing is made of alow friction inert material.

3. The device as claimed in claim 1 wherein the cen-' ter of gravity isnon-coincident with the geometric center so that the device spins aboutan axis parallel to said plane through the upper edge of the measuringchamber when subjected to a magnetic field in the container, due to theaction of centrifugal force upon rotation.

4. The device as claimed in claim 1 wherein the magnetic element issymmetrical about the'center of a truly ellipsoidally-shaped housing andwherein the volume of the measuring chamber cavity is greater than thevolume enclosed between an arcuate trace of the housing adjacent thebase and the base so that the center of gravity is displaced from a truegeometric center whereby the spinning attitude is about an axis parallelto the said plane through the upper edge of the measuring chamber, dueto the action of the centrifugal force upon rotation.

a t a a a

1. A combination weighing and mixing device adapted for use as themixing element of a magnetic stirring apparatus including a containerand magnetic drive means for rotating the mixing element in thecontainer, said device comprising a generally ellipsoidally-shapedhousing, at least one cavity formed in said housing defining a measuringchamber for additives to be mixed with a liquid in the container, saidhousing including a flat base section formed in the housingdiametrically opposed to the measuring chamber and parallel to the planethrough the upper edge of the measuring chamber, and a magnetic elementencapsulated in said housing.
 2. The device as claimed in claim 1wherein said housing is made of a low-friction inert material.
 3. Thedevice as claimed in claim 1 wherein the center of gravity isnon-coincident with the geometric center so that the device spins aboutan axis parallel to said plane through the upper edge of the measuringchamber when subjected to a magnetic field in the container, due to theaction of centrifugal force upon rotation.
 4. The device as claimed inclaim 1 wherein the magnetic element is symmetrical about the center ofa truly ellipsoidally-shaped housing and wherein the volume of themeasuring chamber cavity is greater than the volume enclosed between anarcuate trace of the housing adjacent the base and the base so that thecenter of gravity is displaced from a true geometric center whereby thespinning attitude is about an axis parallel to the said plane throughthe upper edge of the measuring chamber, due to the action of thecentrifugal force upon rotation.